HSRP Version 2

Finding Feature Information

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Information About HSRP Version 2

HSRP Version 2 Design

HSRP version 2 is
designed to address the following restrictions in HSRP version 1:

In HSRP version
1, millisecond timer values are not advertised or learned. HSRP version 2
advertises and learns millisecond timer values. This change ensures stability
of the HSRP groups in all cases.

In HSRP version
1, group numbers are restricted to the range from 0 to 255. HSRP version 2
expands the group number range from 0 to 4095.

HSRP version 2
provides improved management and troubleshooting. With HSRP version 1, you
cannot use HSRP active hello messages to identify which physical device sent
the message because the source MAC address is the HSRP virtual MAC address. The
HSRP version 2 packet format includes a 6-byte identifier field that is used to
uniquely identify the sender of the message. Typically, this field is populated
with the interface MAC address.

The multicast
address 224.0.0.2 is used to send HSRP hello messages. This address can
conflict with Cisco Group Management Protocol (CGMP) leave processing.

Version 1 is the
default version of HSRP.

HSRP version 2 uses
the new IP multicast address 224.0.0.102 to send hello packets instead of the
multicast address of 224.0.0.2, used by HSRP version 1. This new multicast
address allows CGMP leave processing to be enabled at the same time as HSRP.

HSRP version 2
permits an expanded group number range, 0 to 4095, and consequently uses a new
MAC address range 0000.0C9F.F000 to 0000.0C9F.FFFF. The increased group number
range does not imply that an interface can, or should, support that many HSRP
groups. The expanded group number range was changed to allow the group number
to match the VLAN number on subinterfaces.

When the HSRP version
is changed, each group will reinitialize because it now has a new virtual MAC
address.

HSRP version 2 has a
different packet format than HSRP version 1. The packet format uses a
type-length-value (TLV) format. HSRP version 2 packets received by an HSRP
version 1 device will have the type field mapped to the version field by HSRP
version 1 and subsequently ignored.

The Gateway Load
Balancing Protocol (GLBP) also addresses the same restrictions relative to HSRP
version 1 that HSRP version 2 does. See the
Configuring GLBP
document for more information on GLBP.

Jitter timers

Jitter timers are used in HSRP. They are recommended for timers
running on services that work realtime and scale. Jitter timers are intended to
significantly improve the reliability of HSRP, and other FHRP protocols, by
reducing the chance of bunching of HSRP groups operations, and thus help reduce
CPU and network traffic spikes. In the case of HSRP, a given device may have up
to 4000 operational groups configured. In order to distribute the load on the
device and network, the HSRP timers use a jitter. A given timer instance may
take up to 20% more than the configured value. For example, for a hold time set
to 15 seconds, the actual hold time may take 18 seconds.

In HSRP, the Hello timer (which sends the Hello Packet) has a negative
Jitter, while the Holddown timer (which checks for failure of a peer) has a
positive jitter.

How to Configure HSRP Version 2

Changing to HSRP Version 2

HSRP version 2 was introduced to prepare for further enhancements and to expand the capabilities beyond what is possible with HSRP version 1. HSRP version 2 has a different packet format than HSRP version 1.

Note

HSRP version 2 is not available for ATM interfaces running LAN emulation.

HSRP version 2 will not interoperate with HSRP version 1. An interface cannot operate both version 1 and version 2 because both versions are mutually exclusive. However, the different versions can be run on different physical interfaces of the same device. You cannot change from version 2 to version 1 if you have configured groups above the group number range allowed for version 1 (0 to 255).

SUMMARY STEPS

1.enable

2.configureterminal

3.interfacetypenumber

4.ipaddressip-addressmask

5.standbyversion {1 |
2}

6.standby [group-number]
ip [ip-address [secondary]]

7.end

8.showstandby

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configureterminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interfacetypenumber

Example:

Device(config)# interface vlan 400

Configures an interface type and enters interface configuration mode.

Step 4

ipaddressip-addressmask

Example:

Device(config-if)# ip address 10.10.28.1 255.255.255.0

Sets an IP address for an interface.

Step 5

standbyversion {1 |
2}

Example:

Device(config-if)# standby version 2

Changes the HSRP version.

Step 6

standby [group-number]
ip [ip-address [secondary]]

Example:

Device(config-if)# standby 400 ip 10.10.28.5

Activates HSRP.

The group number range for HSRP version 2 is 0 through 4095. The group number range for HSRP version 1 is 0 through 255.

Step 7

end

Example:

Device(config-if)# end

Ends the current configuration session and returns to privileged EXEC mode.

RFCs

RFCs

Title

RFC 792

Internet Control Message Protocol

RFC 1828

IP Authentication Using Keyed MD5

RFC 2281

Cisco Hot Standby Router Protocol

Technical Assistance

Description

Link

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Feature Information for HSRP
Version 2

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Table 1 Feature Information for HSRP
Version 2

Feature Name

Releases

Feature
Information

HSRP Version
2

12.3(4)T

HSRP Version
2 feature was introduced to prepare for further enhancements and to expand the
capabilities beyond what is possible with HSRP version 1. HSRP version 2 has a
different packet format than HSRP version 1.

In Cisco IOS
XE Release 3.5S, support was added for the Cisco ASR 903 Router.

The following
commands were introduced or modified by this feature:
showstandby,
standbyip,
standbyversion.